# std::stack

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< cpp‎ | container

Defined in header `<stack>` |  |
template< class T, class Container = std::deque<T> > class stack; |  |

The `std::stack` class is a container adaptor that gives the programmer the functionality of a stack - specifically, a LIFO (last-in, first-out) data structure.

The class template acts as a wrapper to the underlying container - only a specific set of functions is provided. The stack pushes and pops the element from the back of the underlying container, known as the top of the stack.

### Template parameters

T | - | The type of the stored elements. The program is ill-formed if `T` is not the same type as `Container::value_type`.
Container | - | The type of the underlying container to use to store the elements. The container must satisfy the requirements of SequenceContainer. Additionally, it must provide the following functions with the usual semantics: `back()`, e.g., std::vector::back(), `push_back()`, e.g., std::deque::push_back(), `pop_back()`, e.g., std::list::pop_back(). The standard containers std::vector (including `std::vector<bool>`), std::deque and std::list satisfy these requirements. By default, if no container class is specified for a particular stack class instantiation, the standard container std::deque is used.

### Member types

Type | Definition
`container_type` | `Container`
`value_type` | `Container::value_type`
`size_type` | Container::size_type
`reference` | `Container::reference`
`const_reference` | `Container::const_reference`

### Member objects

Member | Description
Container c | the underlying container (protected member object)

### Member functions

(constructor) | constructs the `stack` (public member function)
(destructor) | destructs the `stack` (public member function)
operator= | assigns values to the container adaptor (public member function)
##### Element access
top | accesses the top element (public member function)
##### Capacity
empty | checks whether the container adaptor is empty (public member function)
size | returns the number of elements (public member function)
##### Modifiers
push | inserts element at the top (public member function)
push_range (C++23) | inserts a range of elements at the top (public member function)
emplace (C++11) | constructs element in-place at the top (public member function)
pop | removes the top element (public member function)
swap (C++11) | swaps the contents (public member function)

### Non-member functions

operator==operator!=operator<operator<=operator>operator>=operator<=> (C++20) | lexicographically compares the values of two `stack`s (function template)
std::swap(std::stack) (C++11) | specializes the std::swap algorithm (function template)

### Helper classes

std::uses_allocator<std::stack> (C++11) | specializes the std::uses_allocator type trait (class template specialization)
std::formatter<std::stack> (C++23) | formatting support for `std::stack` (class template specialization)

### Deduction guides | (since C++17)

### Notes

Feature-test macro | Value | Std | Feature
--- | --- | --- | ---
`__cpp_lib_containers_ranges` | `202202L` | (C++23) | Ranges construction and insertion for containers

### Example

| This section is incomplete Reason: no example

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 307 | C++98 | `Container` could not be `std::vector<bool>` | allowed
LWG 2566 | C++98 | Missing the requirement for `Container::value_type` | ill-formed if `T` is not the same type as `Container::value_type`

### See also

vector | dynamic contiguous array (class template)
vector<bool> | space-efficient dynamic bitset (class template specialization)
deque | double-ended queue (class template)
list | doubly-linked list (class template)

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